Using DNA analyses for classification

Dr Patrick Brownsey and Dr Leon Perrie from Te Papa explain the effect DNA analysis is having on our understanding of fern evolutionary history and how taxonomic classification changes as a result.

Jargon alert: Fern allies are groups of plants that are not true ferns but share some fern characteristics including spore dispersal and gametophyte and sporophyte generations.

Transcript

Dr Patrick Brownsey

Taxonomy is the science of classification. It’s trying to sort out, for the human mind, the array of diversity that we see out there in nature. Originally, we were reliant just on morphological characters, and that has given us a really good basis for classifying ferns, but then other technologies have come along, such as the scanning electron microscope that enabled us to look in detail at spore patterns and spore structures and other close-up features.

Most recently, it’s the DNA technology that has come along that enables us to sequence DNA and see the pattern of nucleotides in the DNA, and that gives us a much finer technique for determining how closely related different species are. And there is a whole lot of analysis that you can do around that that tells you a great deal about the evolution and the relationships of different species. It’s a very powerful technology.

Dr Leon Perrie

With DNA work, we have been able to get a better idea of how things are related. We have learnt more about the evolutionary history of plants and animals. As we’ve updated our understanding of how plants and animals are related to one another, we’ve had to change the taxonomic classification in order to reflect that improved updated understanding of their evolutionary history.

A great example within the fern type of plants is that there are several small groups of plants which used to be regarded as fern allies. In particular, there is the Tmesipteris fork ferns. They were previously grouped with plants like Lycopodium and Selaginella in the fern allies, but with DNA analyses, people have worked out that Tmesipteris fork ferns they are actually more related, more closely related to ferns. So they are now regarded as ferns, rather than as fern allies.

Acknowledgements Australasian Pollen & Spore Atlas http://creativecommons.org/licenses/by-nc-sa/3.0/ Museum of New Zealand Te Papa Tongarewa